Early diagnosis and advances in treatment are resulting in longer survival of HIV-positive (HIV+) children. New approaches to primary prenatal infection are also resulting in larger numbers of HIV-negative (HIV-) children being born to HIV+ mothers. Each year, cohorts from these vulnerable populations of "HIV-affected" children are beginning school, a stressful developmental transition. Concerns for the health, well-being, and adjustment of hIV-affected children during this transition are raised by evidence that some healthy children entering kindergarten show increased susceptibility to infectious diseases and other adverse outcomes. As a consequence, families, educators, and health professionals must make informed ethical and programmatic decisions for hIV+ children beginning school. However, almost nothing is known about the behavioral and biologic outcomes of school entry for those vulnerable children. To address this need, we propose a longitudinal study of HIV-affected children entering kindergarten. We will: . Examine differences in behavioral and biologic outcomes after primary school entry among HIV+ and HIV- children of hIV+ mothers, and HIV- children of HIV- mothers (marched for race, gender, and school). . Asses the extent to which the severity of HIV disease in HIV+ children affects behavioral an biologic outcomes following school entry. . Determine whether outcomes following school entry are also affected, independent of hIV serostatus, by characteristics of the family school entry. . Examine the degree to which physiologic reactivity modifies the relation of family stress to behavioral and biologic outcomes following school entry in hIV+ and HIV- children of HIV+ mothers. We will follow a cohort that is recruited in three successive years from children entering kindergarten in 1997, 1998, and 1999. Each child will be followed for six months. The cohort will consist of three groups; asymptomatic HIV+ children of HIV+ mothers (N=55), healthy HIV- children of hIV+ mothers (N=55), and healthy HIV- children of HIV+ children of HIV- mothers (N=110) matched by race, gender, and school to the HIV-affected children. The effect of school entry on behavioral outcomes (behavior problems, psychiatric morbidity, and attitude toward school) and biologic outcomes (injuries, respiratory illness incidence, and decline in immune function) will be evaluated. Possible predictors of response to school entry will be measured at the level of hIV status (seropositivity, immune status, and viral burden), the family /stressors/supports, family context, and health behavior), and the child (school readiness, resilience/vulnerability, and psychobiologic reactivity).